Search Results (69)

The construction sector presently consumes about 40% of global energy and generates 36% of CO₂ emissions, making facade retrofits a priority for decarbonising buildings. This review clarifies how ventilated facades (VFs), wall assemblies that interpose a ventilated air cavity between outer cladding and the insulated structure, address that challenge. First, the paper categorises VFs by structural configuration, ventilation strategy and functional control into four principal families: double-skin, rainscreen, hybrid/adaptive and active–passive systems, with further extensions such as BIPV, PCM and green-wall integrations that couple energy generation or storage with envelope performance. Heat-transfer analysis shows that the cavity interrupts conductive paths, promotes buoyancy- or wind-driven convection, and curtails radiative exchange. Key design parameters, including cavity depth, vent-area ratio, airflow velocity and surface emissivity, govern this balance, while hybrid ventilation offers the most excellent peak-load mitigation with modest energy input. A synthesis of simulation and field studies indicates that properly detailed VFs reduce envelope cooling loads by 20–55% across diverse climates and cut winter heating demand by 10–20% when vents are seasonally managed or coupled with heat-recovery devices. These thermal benefits translate into steadier interior surface temperatures, lower radiant asymmetry and fewer drafts, thereby expanding the hours occupants remain within comfort bands without mechanical conditioning. Climate-responsive guidance emerges in tropical and arid regions, favouring highly ventilated, low-absorptance cladding; temperate and continental zones gain from adaptive vents, movable insulation or PCM layers; multi-skin adaptive facades promise balanced year-round savings by re-configuring in real time. Overall, the review demonstrates that VFs constitute a versatile, passive-plus platform for low-carbon buildings, simultaneously enhancing energy efficiency, durability and indoor comfort. Future advances in smart controls, bio-based materials and integrated energy-recovery systems are poised to unlock further performance gains and accelerate the sector’s transition to net-zero. Emerging multifunctional materials such as phase-change composites, nanostructured coatings, and perovskite-integrated systems also show promise in enhancing facade adaptability and energy responsiveness. Full article

Building facade insulation technologies have evolved from primitive thermal barriers to high-performance, multifunctional systems that enhance energy efficiency and indoor comfort. Historical insulation methods, such as thick masonry walls and timber-based construction, have gradually been replaced by advanced materials and innovative facade designs. Studies indicate that a significant proportion of a building’s heat loss occurs through its external walls and windows, highlighting the need for effective insulation strategies. The development of double-skin facades (D-SFSs), adaptive facades (AFs), and green facades has enabled substantial reductions in heating and cooling energy demands. Materials such as vacuum insulation panels (VIPs), aerogels, and phase change materials (PCMs) have demonstrated superior thermal resistance, contributing to improved thermal regulation and reduced carbon emissions. Green facades offer additional benefits by lowering surface temperatures and mitigating urban heat island effects, while D-SF configurations can reduce cooling loads by over 20% in warm climates. Despite these advancements, challenges remain regarding the initial investment costs, durability, and material sustainability. The future of facade insulation technologies is expected to focus on bio-based and recyclable insulation materials, enhanced thermal performance, and climate-responsive facade designs. This study provides a comprehensive review of historical and modern facade insulation technologies, examining their impact on energy efficiency, sustainability, and future trends in architectural design. Full article

Thermal comfort in public buildings is crucial for occupant well-being and energy efficiency. This study employs TRNSYS software to simulate the effects of thermal mass, window performance, and window–wall ratio (WWR) on summer thermal comfort. The results indicate that without energy-saving measures, increased thermal mass raises daily average maximum and minimum temperatures by 0.33–0.96 °C and 0.14–0.94 °C, respectively. Enhanced WWRs lead to higher daily average maximum and minimum temperatures for double-glazed windows (0.18–0.61 °C and 0.07–0.62 °C, respectively), while single-glazed windows show increased maximum temperatures (0.18–1.86 °C) but decreased minimum temperatures (−0.01 to −0.72 °C). Thermal mass has a modest effect on indoor overheating during high outdoor temperatures. Double-glazed windows and lower WWRs effectively reduce indoor overheating, decreasing the attenuation coefficient by 2.13–28.94%. Conversely, single-glazed windows and higher WWRs enhance heat dissipation, increasing daily average temperature fluctuations by 2.33–44.18%. Notably, single-glazed windows with WWRs ≥ 50% improve thermal comfort by reducing extreme superheat temperature occurrence in heavy-thermal-mass buildings by 0.81 to 14.63%. Despite lower cooling loads with heavy thermal mass, double-glazed windows, and low WWRs, the study suggests that single-glazed windows and high WWRs can enhance summer thermal comfort. Therefore, reasonable shading measures and lighter thermal mass are recommended for such buildings. Full article

With the increasing demand for energy-efficient and sustainable building materials, innovative cooling technologies have become a key focus in the construction industry. This study developed a double-layer cooling coating integrating evaporation and radiation mechanisms. The first layer consists of a TiO₂/PUA radiation layer, where rutile TiO₂ is incorporated into polyurethane acrylate (PUA) resin to enhance solar reflectivity. The second layer is a P(NVP-co-NMA) hydrogel, which evaporates water at high temperatures and absorbs moisture from the air at low temperatures, eliminating the need for additional water supply systems. The TiO₂/PUA@P(NVP-co-NMA) coating demonstrates high solar reflectivity and infrared emissivity, effectively reducing indoor temperatures by dissipating heat through water evaporation and radiative cooling. Testing showed a temperature reduction of approximately 7.6 °C in a small house with this coating under simulated conditions. This material demonstrates favorable properties that may make it suitable for applications on building roofs and exterior walls, potentially addressing some limitations of conventional evaporative or radiative cooling systems. Its observed multi-effect cooling performance indicates promise for contributing to energy savings in sustainable building designs. Full article

Wineries require a significant energy demand for cooling interior spaces. As a result, designing energy-efficient winery buildings has become a crucial concern for winemaking countries. The objective of this study was to evaluate six winery building models with bioclimatic designs, located in the Guadalupe Valley, Baja California, using data on thermal performances (indoor temperature and relative humidity) and energy consumption obtained through dynamic thermal simulation. A baseline winery building model was developed and then enhanced with bioclimatic strategies: a semi-buried building; an underground cellar; an underground cellar with the variants of a green roof, double roof, shaded walls, and polyurethane insulation. The last solution entailed the requirement of a reduction in cooling in the warm season by 98 MWh, followed by the one with a green roof, corresponding to 94 MWh. This study provides valuable insights into the effectiveness of different architectural approaches, offering guidelines for the design of functional buildings for wine production, besides presenting energy-efficient solutions for wineries tailored to the climatic conditions of the study region. These findings highlight the importance of a function-based and energy-efficient architectural design in the winemaking industry, which leads to the definition of buildings with a compact arrangement of the functional spaces and a fruitful integration of the landscape through a wise adoption of underground solutions. Full article

A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in a multi-jet configuration to focus on the region that falls between the two consecutive fluidic oscillators and, hence, suggest a mechanism to uniformly cool the targeted flat surface. A comparative experimental study of dual sweeping jets (DSJs), double sweeping jets (DbSJs), and double circular jets (DbCJs) was conducted at different jet-to-plate spacings, various Re numbers, and three aspect ratios. The multi-circular and sweeping jets were impinged on a flat hot surface, which was heated at a constant flux of current, and thermocouples were employed to efficiently collect the time-averaged heat transfer distribution along the sweeping and transverse directions. It was determined that heat transfer, in terms of the Nusselt number, generally increased with increasing Re number and reduced the jet-to-wall spacing for the DSJ, DbSJ, and DbCJ, with some minor exceptions. The relative performance of these fluidic devices suggested that the best performance of DSJ was at small spacing and higher Re, DbSJ at moderate spacing and lower Re, and DbCJ at moderate spacing and moderate Re. The mutual comparison showed that along the sweeping motion, in the central region, DbCJ was better than both DSJ and DbSJ; in the right region, DSJ performance was far better than DbCJ and DbSJ; in the left region, DSJ was better than DbSJ when comparing the respective centers of DSJ and DbSJ. The dominance of DSJ over DbSJ at the centers of their respective bodies even extends in the transverse direction. Finally, for higher aspect ratios, the DSJ performed better in the outer regions, while the DbSJ performed well in the central region. Similarly, for both DSJ and DbSJ unanimously, the effect of changing the aspect ratio is interesting as initially, the Nu values increase for a higher aspect ratio, but by increasing the AR further, it causes a divergence of the fluidic volume from the central region to the surrounding region. Full article

In semiconductor inspection equipment, a chuck used to hold a wafer is equipped with a cooling or heating system for temperature uniformity across the surface of the wafer. Surface temperature uniformity is important for increasing semiconductor inspection speed. Triply periodic minimal surfaces (TPMSs) are proposed to enhance temperature uniformity. TPMSs are a topic of increasing research in the field of additive manufacturing and are a type of metamaterial inspired by nature. TPMSs are periodic surfaces with no intersections. Their continuous curve offers self-support during the additive manufacturing process. This structure enables the division of a single space into two domains. As a result, the heat transfer area per unit volume is larger than that of general lattice structures, leading to a superior heat transfer performance. This paper proposes a new structure called a double-wall TPMS. The process of creating a double-walled TPMS by adjusting the thickness of the sheet TPMS was investigated, and its thermal performance was studied. Finally, a double-wall TPMS was applied to the chuck. The optimal designs for the diamond and gyroid structures exhibited a difference in surface temperature uniformity of 0.23 °C and 0.66 °C, respectively. Accordingly, the models optimized with the double-wall TPMS are proposed. Full article

Narrow-gap arc welding is an efficient method that significantly enhances industrial production efficiency and reduces costs. This study investigates the application of low-alloy steel wire EG70-G in narrow-gap gas metal arc welding (GMAW) on thick plates. Experimental observations were made to examine the arc behavior, droplet transition behavior, and weld formation characteristics of double-wire welding under various process parameters. Additionally, the temperature field of the welding process was simulated using finite element software (ABAQUS 2020). Finally, the microstructure and microhardness of the fusion zone in a double-wire, single-pass filled joint under the different welding speeds were compared and analyzed. The results demonstrate that the use of double-wire GMAW in narrow-gap welding yielded positive outcomes. Optimal settings for wire feeding speed, welding speed, and double-wire lateral spacing significantly enhanced welding quality, effectively preventing side wall non-fusion and poor weld profiles in the welded joints. The microstructure of the fusion zone produced at a higher welding speed (11 mm/s) was finer, resulting in increased microhardness compared to welds obtained at a lower speed (8 mm/s). This is attributed to the shorter duration of the liquid molten pool and the faster cooling rate associated with higher welding speed. This research provides a reference for the practical application of double-wire narrow-gap gas metal arc welding technology. Full article

This study investigates the implementation of passive design strategies to improve the thermal environment in the extremely hot climates of Brazil, Portugal, and Turkey. Given the rising cooling demands due to climate change, optimizing energy efficiency in buildings is essential. Using the Trace 3D Plus v6.00.106 software, typical residential buildings for each country were simulated to assess various passive solutions, such as building orientation, wall and roof modifications, glazing optimization options, window-to-wall ratio (WTWR) reduction, shading, and natural ventilation. The findings highlight that Brazil experienced the higher discomfort temperatures compared to Mediterranean climates, with indoor air temperatures exceeding 28 °C all year round and remaining between 34 °C and 37 °C for nearly 40% of the time. Building orientation had a minimal impact near the equator, while Mediterranean climates benefited from an up to 10% variation in energy demand. Thermal insulation combined with white exterior paint resulted in Şanlıurfa experiencing annual energy savings of up to 26%. Optimal roof solutions yielded a 19% demand reduction in Évora, while WTWR reduction and double-colored glazing achieved up to a 35% reduction in Évora and 19% in other regions. Combined strategies achieved energy demand reductions of 44% for Évora, 40% for Şanlıurfa, and 32% for Teresina. The study emphasizes the need for integrated, climate-specific passive solutions, showing their potential to enhance both energy efficiency and the thermal environment in residential buildings across diverse hot climates. Full article

Lightweight concrete offers numerous advantages for modular construction, including easier construction planning and logistics, and the ability to offset additional dead loads induced by double-wall and double-slab features. In a previous study, authors proposed incorporating lightweight aggregate into foamed concrete instead of adding extra foam to achieve lower density, resulting in lightweight concrete with an excellent strength-to-density ratio. This paper further investigated the performance aspects of foamed concrete with lightweight aggregate beyond mechanical strength. To evaluate the effect of aggregate type and foam content, three mix compositions were designed for the lightweight concrete. Specimens were prepared for experimental tests on thermal conductivity and drying shrinkage of lightweight concrete. Results showed that while both the increase in foam volume and the incorporation of lightweight aggregate led to higher drying shrinkage, they also contributed to improved insulating properties and reduced potential of cracking. Using typical multi-storey modular residential buildings in Hong Kong and three other Chinese cities as case studies, simulations were performed to assess potential savings in annual cooling and heating loads by employing the proposed lightweight concrete. These findings demonstrate the practical benefits of using foamed concrete with lightweight aggregate in modular construction and provide valuable insights for further optimization and implementation. Full article

Gas turbines are widely applied in many fields, and blade cooling is a key way to improve gas turbines’ power and efficiency. In order to explore a high-efficiency cooling method, a new variant configuration with unique coolant supply passage arrangements is proposed and explored in this paper. The numerical simulation method of solving the Navier–Stokes equations is used after mesh independence calculation and turbulence model validation. The results show that the variant structure has better streamlines distribution with double vortex flows in both the inner and outer chambers. Compared to the original configuration, the heat transfer intensity in the outer chamber is improved, and the globally averaged Nusselt number is 17.1% larger. The case with uniformly distributed nozzles has the best flow and heat transfer performance. As the nozzle number increases, the total pressure loss and friction coefficient decrease, but the heat transfer increases first and then decreases. The case of three nozzles has the best comprehensive cooling behavior. The aspect ratio has important influences on the double-vortex cooling configuration. Cases with small aspect ratios have higher local heat transfer intensity, but the flow loss is larger. The case with aspect ratio 4 has the best cooling performance. Full article

The spatiotemporal evolution of the flow structures and coolant coverage of double-row film cooling with upstream forward jets and downstream backward jets, having a significant impact on film-cooling performance, is studied using the simplified thermal lattice Boltzmann method (STLBM). Moreover, the effect of the inclination angle of downstream backward jets is considered. The high-performance simulations of film cooling have been conducted by using our verified in-house solver. Results show that special flow structures, such as a sand dune-shaped protrusion, appear in double-row film cooling with upstream forward jets and downstream backward jets, which is mainly because of the blockage effect resulting from the coolant jet with backward injection. The interaction among structures results in the generation of an anti-counterrotating vortex pair (anti-CVP). The anti-CVP with the downwash motion can result in the attachment of coolant to the bottom wall, which promotes the stability and lateral coverage of coolant film. The momentum and heat transport are strengthened as the backward jet is injected into the boundary layer of the mainstream. Although the downstream evolution of the backward jet is not very smooth, its core attaches closely to the bottom wall due to the downwash motion of anti-CVP. Moreover, there is an obvious backflow zone shown in the trailing edge of the downstream backward jet with a large inclination angle. The obvious backflow makes the coolant attach to the bottom wall well. Therefore, the film cooling effectiveness is improved as the inclination angle of the downstream backward jet varies from ${\alpha }_{down}=135°$ to ${\alpha }_{down}=155°$, with a constant blowing ratio of $BR=0.5$. In addition, the fluctuation of the bottom wall’s temperature is weak due to the stable coverage of the coolant layer under ${\alpha }_{down}=155°$. The film-cooling performance with an inclination angle of ${\alpha }_{down}=155°$ is the best among all the cases studied in this work. This work provides essential insights into film cooling with backward coolant injection and contributes to obtaining a complete understanding of film cooling with backward coolant injection. Full article

In the context of global warming, the focus on applying and researching double–skin facade (DSF) systems to reduce energy consumption in buildings has significantly increased. However, researchers have not thoroughly examined the performance and applicability of DSFs in severe cold regions with high winter heating demands. This study aims to evaluate the potential application of DSFs in the harsh cold cities of Northwest China and investigate their role in enhancing energy efficiency in large public buildings. Through energy consumption simulation and a comprehensive evaluation using the TOPSIS entropy weight method, the effects of applying 20 DSF schemes in four cold cities in Xinjiang (Kashgar, Urumqi, Altay, and Turpan) were analyzed. The experimental results indicate that the average EUI energy–saving rates in Kashgar, Urumqi, Altay, and Turpan are 64.75%, 63.19%, 56.70%, and 49.41%, respectively. South–facing orientation is deemed optimal for DSF in Xinjiang cities, with the highest energy–saving rate reaching 15.19%. In Kashgar, the energy–saving benefits of west–facing DSF surpass those of north–facing DSF. Conversely, the order of orientation benefits for other cities is south, north, west, and east. An analysis of heating, cooling, and lighting energy consumption reveals that Box Windows exhibit superior heating energy efficiency, while Corridors are more effective for cooling. This characteristic is also evident in the optimal installation orientation of various types of curtain walls. Given the relatively higher demand for heating compared to cooling in urban areas, Box Windows yields significant benefits when facing south, west, or north; conversely, if there is a high demand for urban cooling, Corridors should be considered in these three directions. Multistorey DSF systems are suitable for east–facing buildings in Xinjiang cities. Selecting suitable DSF schemes based on specific conditions and requirements can reduce building energy consumption. The research findings offer theoretical guidance for designing and implementing DSF in diverse cities in cold regions. Full article

The energy consumption levels of buildings in the United Arab Emirates (UAE) are among the highest in the world. One of the main reasons for this energy consumption is the need to cool buildings due to the hot climate of the UAE. As a large part of the heat accumulated inside buildings comes from windows, in this study, the effects of window size and direction in a typical building in the UAE on energy consumption and thermal performance are investigated through numerical modeling. The modeling process includes thermal conductivity, thermal convection, and solar radiation simulation. The energy performance of any building at any location can be obtained based on local weather data and the computational thermal characteristics of the building elements, such as its walls, roofs, windows, and doors. The study covered all different seasons of the year and different orientations for the windows, allowing the daily and yearly energy consumption associated with the windows to be obtained. Furthermore, the energy consumption was obtained for solar radiation and heat gain separately for both single- and double-glazed windows. It was found that north-facing windows consume significantly less annual energy (36% less), when compared with windows facing in the other three directions. Furthermore, the east- and west-facing windows consumed about 41% and 35% more daily cooling energy in August, when compared to north- and south-facing windows, respectively. The use of a window with a height equal to that of the wall can cause a clear greenhouse effect; hence, it is recommended to limit the window’s height to two-thirds of the wall height, which can save about one-third of the associated yearly cooling energy. This study should be considered as a general guideline, as the thermal performance of any specific building will be affected by its own thermal characteristics. Full article

Purpose—This study aims to perform an in-depth analysis of double-diffusive natural convection (DDNC) in an irregularly shaped porous cavity. We investigate the convective heat transfer process induced by the lower wall treated as a heat source while the side walls of the enclosure are maintained at a lower temperature and concentration, and the remaining wall is adiabatic. Various factors, such as the Rayleigh number, Darcy effects, Hartmann number, Lewis number and effects of magnetic inclination are evaluated for their influence on flow dynamics and heat distribution. Design/methodology/approach—After validating the results, the FEM (finite element method) is used to simulate the flow pattern, temperature variations, and concentration by solving the nonlinear partial differential equations with the modified Rayleigh number (10⁴ ≤ Ra ≤ 10⁷), Darcy number (10⁻⁴ ≤ Da ≤ 10⁻¹), Lewis number $(0.1\le Le\le 10)$, and Hartmann number $\left(0\le Ha\le 40\right)$ as the dimensionless operating parameters. Findings—The finding shows that the patterns of convection and the shape of the isotherms within porous enclosures are notably affected by the angle of the applied magnetic field. This study enhances our understanding of how double-diffusive natural convection (DDNC) operates in these enclosures, which helps improve heating and cooling technologies in various engineering fields. Research limitations/implications—Numerical and experimental extensions of the present study make it possible to investigate differences in thermal performance as a result of various curvatures, orientations, boundary conditions, and the use of three-dimensional analysis and other working fluids. Practical implications—The geometry configurations used in this study have wide-ranging applications in engineering fields, such as in heat exchangers, crystallization, microelectronics, energy storage, mixing, food processing, and biomedical systems. Originality/value—This study shows how an inclined magnetic field affects double-diffusive natural convection (DDNC) within a porous system featuring an irregularly shaped cavity, considering various multiphysical conditions. Full article